Ventilated cage and open rack system

ABSTRACT

A wire bar lid for use in an animal cage is provided having a thin perimeter having a substantially rectangular cross-section. A plurality of wires are supported within the perimeter below the plane of the perimeter.

This is a continuation of U.S. patent application Ser. No. 07/596,808,filed on Oct. 12, 1990 and is now U.S. Pat. No. 5,165,362 which is acontinuation-in-part of Ser. No. 07/515,803 which was filed on Apr. 27,1990 and is now U.S. Pat. No. 4,989,545.

BACKGROUND OF THE INVENTION

This invention is directed to a ventilated cage and rack system, andmore particularly to an open rack system which provides protection forboth personnel attending to the system and animals contained within thecage from contamination by reducing cross cage contamination.

Ventilated cage and rack systems are well known in the tart. One suchventilated cage and rack system is disclosed in U.S. Pat. No. 4,365,590assigned to Lab Products, Inc. in which a closed rack system including aplurality of shelves each having a door for each shelf is provided, Eachshelf compartment is sized to contain horizontally spaced animal cageshaving open top ends spaced well below the ceiling of the shelfcompartment. A low pressure air plenum extends along one side of therack system to provide air to each of the shelves. The opposed side ofeach shelf has filtered air port openings which communicate with theroom interior to provide a low pressure negative air flow across the topopen ends of the animal cages. This cage and rack system also provides awatering system in which a water valve connected to a common watermanifold extends into the cage to allow animals to drink therefrom.

The prior art ventilated cage and rack system was satisfactory. However,it suffered from the deficiencies that it can not provide a cage levelbarrier as the barrier was breached by the insertion of the valvecoupled to the main watering system each time the cage was removed fromthe rack system and then re-inserted into the rack system. Additionally,the air flow for a single cage could not be controlled. Accordingly,inadequate personnel protection is provided by this ventilated cage andrack system.

One such solution to the cage barrier problem was to provide a quickdisconnect valve within the ventilated cage and rack system so that thecage and the drinking valve could be disconnected from the rack whilemaking it possible to maintain the drinking valve within the same cageat all times, thus preventing cross contamination due to reinsertion ofthe drinking valve. Additionally, a positive air pressure plenumprovides positive air pressure through the cage in addition to thenegative air flow across the tops of the cages.

This ventilated cage and rack system was also satisfactory. However, italso suffered from the disadvantage that no personnel protection wasprovided when the rack doors were opened. Furthermore, it was found thatto provide the negative air plenum and positive air plenum that a greatdeal of air was required to move an air column along the large spacebetween the cage top and the bottom of the next highest shelf.Accordingly, amounts of energy and high air velocities were required tomove the column of air across the cage tops.

The cages used in the prior art system have a filtered top and gasimpermeable bottom which are closed in a petri dish manner. The top isformed with a lip which rests on and overhangs the bottom. A wire barlid is disposed between the top and bottom to contain the animal in thecage as well as hold a water bottle and/or feed in an animal accessibleposition. The conventional lid includes a wire frame having a circularcross-section with lateral wire rods welded to the frame, creating a 1/4inch gap between the filter top and cage bottom. Air passes through thegap created at the meeting point of this top and bottom lettingcontaminated air out and letting outside air within the cage. However,when a positive pressure air flow is provided within the cage this gapallows bedding and debris to be discharged from the cage by the activityof the animals contained with the cage. Accordingly, cross contaminationcan occur when two cages are positioned adjacent each other on theshelf. Additionally, personnel contamination occurs as the contaminatedgases pass from the cages to the rack.

One attempt to cure this cross contamination problem is known in U.S.Pat. No. 4,343,261 in which all air flow is directed entirely throughthe filter of a cage top positioned in the rack. However, this cage andrack system suffers from the disadvantage of forcing contaminantsdisposed on the filter top into the cage.

Accordingly, it is desired to provide a ventilated cage and rack systemwhich overcomes the shortcomings of the prior art by combining bothpersonnel protection and animal protection at a cage level barrier whiledecreasing the volume of air and energy required to do so.

SUMMARY OF THE INVENTION

Generally speaking, in accordance with the instant invention, aventilated cage and rack system for providing air ventilation directlyto the animals within a cage level barrier is provided. The rackincludes a plurality of shelves, each shelf is formed as an air plenumso that air may travel within the shelf to a plurality of predeterminedpositions within the rack. At least one cage level barrier having afilter bonnet is positioned on a shelf, so that the shelf removes airdisposed adjacent the bonnet. A cage guide formed in substantially thesame shape as the bonnet is affixed to the bottom of the shelf so thatwhen the barrier cage is placed within the ventilated rack, it ispositioned within the cage guide. The cage guide is separated from thebonnet by a relatively small distance. The air plenum shelf is providedwith a negative pressure to remove gases from above the cage bonnet.

In another embodiment of the invention, an air diffuser is disposedwithin the sidewall of the cage bottom. A positive air pressure plenumsupplies air to a plurality of predetermined positions along each shelfwithin the rack. The positive pressurized air is passed from thepositive air pressure plenum to the cage through the air diffuser.

In another embodiment of the invention, the shelf air plenum is apositive air plenum. Air passes through the air plenum to push air aboutthe cage bonnet away f rom the bonnet thereby continuously removing theexhaust air from the cage.

Yet another embodiment includes a water manifold contained within thepositive air plenum to provide water at the predetermined position alongthe shelf. A drinking valve disposed within the air diffuser receivesthe water. A quick release coupling connects the water manifold with thedrinking valve.

A lid is provided having a flat (rectangular cross-sectioned) frame forresting on the cage bottom. A skirt integrally formed with the frameextends therefrom at a substantially right angle. A flange extends fromthe skirt. A plurality of metal rods are mounted on the flange away fromthe frame.

Accordingly, it is an object of the instant invention to provide animproved ventilated cage and rack system.

Another object of the invention is to provide a cage level barrier cagewhich reduces cross contamination between cages.

A further object of the invention is to provide a ventilated cage andrack system which provides both personnel protection and animalprotection at a cage level barrier.

Another object of the invention is to provide an open rack ventilatedcage and rack system.

Still another object of the invention is to provide a simplifiedventilated cage and rack system in which each shelf acts as an exhaustplenum for the cages located below it and as a shelf support for thecages located above it.

Yet another object of the invention is to provide a ventilated cage andrack system in which a cage may be removed without affecting theoperation of the remaining cages.

A further object of the invention is to provide a lid which reduces thegap between cage top and cage bottom.

Still another object of the invention is to provide a lid which preventsbedding and debris kicked up by animals within the cage from exiting thecage.

Still other objects and advantages of the invention will in part beobvious and in part be apparent from the specification.

The invention accordingly comprises the features of construction,combination of elements, and arrangements of parts which will beexemplified by the constructions hereinafter set forth and the scope ofthe invention will be indicated in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention,, reference is had to thefollowing description taken in connection with the accompanyingdrawings, in which:

FIG. 1 is a front elevational view of the ventilated cage and racksystem constructed in accordance with a preferred embodiment of theinvention;

FIG. 1a is a top plan view taken through line 1a-1a of FIG. 1;

FIG. 2 is a partial sectional view of the ventilated cage and racksystem constructed in accordance with the invention;

FIG. 3 is an enlarged sectional view of an air plenum constructed inaccordance with the invention;

FIG. 4 is an enlarged sectional view of a cage positioned within theventilated cage and rack system constructed in accordance with a secondembodiment of the invention;

FIG. 5 is an enlarged front elevational view showing the cage of FIG. 1;

FIG. 6 is a sectional view taken along line 6--6 of FIG. 1;

FIG. 7 is a sectional view of a water manifold and air plenumconstructed in accordance with the invention;

FIG. 8 is a sectional view showing the water manifold and air plenum ofFIG. 7 in a docking position;

FIG. 9 is a sectional view of an air plenum constructed in accordancewith the invention;

FIG. 10 is a fragmented sectional view of the docking mechanism for theair plenum in a docked position;

FIG. 11 is a side elevational view of a wire bar lid constructed inaccordance with the invention supported within a cage;

FIG. 12 is a sectional view taken along line 12--12 of FIG. 11;

FIG. 13 is a sectional view taken along line 13--13 of FIG. 11; and

FIG. 14 is a sectional view taken along line 14--14 of FIG. 12.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference is first made to FIGS. 1 and 2 wherein a ventilated cage andrack system, generally indicated at 10, constructed in accordance withthe invention is shown. Ventilated cage and rack system 10 includes anopen rack 12 having a frame including corner posts 11 which areconnected to each other and supported by each other by a cross bar 13positioned between adjacent corner posts 11. The opposed side of rack 10includes a wall forming exhaust plenum 16 extending parallel to cornerpost 11. A plurality of shelves 14 are disposed in parallel betweencorner posts 11 and rack exhaust plenura 16.

A plurality of cage level barriers 20 (cages 20) are positioned withinrack 12 on shelves 14. Each cage 20 is formed of a gas impermeablebottom portion 22 having an upstanding sidewall 50 and a filter bonnet24. Bonnet 24 having a lip 28 is an open top bonnet having a filtertherein of the type disclosed in U.S. Pat. No. 4,480,587. Cages 20 arepositioned within rack 12 by canopy guides 26. Canopy guides 26 extendfrom the bottom of each shelf 14 and are positioned in pairs across adistance slightly less than the width of cages 20 canopy guides 26 areshaped to substantially parallel the shape of bonnet 24, so that alongwith shelf 14 to form a small gap h sufficient to allow movement ofgases between canopy guide 26 and bonnet 24 is present. In an exemplaryembodiment, gap h is 3/16 of an inch to 1/4 of inch. Canopy guides 26profile bonnet 24 and overlap a bottom lip 28 of bonnet 24 creating atension fit against the sidewall of bonnet 20. One end of canopy guide26 is fixed to rack 12 (FIG. 5) while the other end of canopy 26 is freefloating along the horizontal direction and spaced from an adjacentcanopy 26 by a spring 30 to allow easy positioning of cage 20 withincanopy guides 26.

Since canopy 26 surrounds bonnet 24 including lip 28 canopy 26effectively isolates bonnet 24 from the remainder of the cage.Accordingly, any gases passing from cage 20 around lip 28 remain incanopy 26 until removed by a shelf plenum 14. Additionally, because lip28, is contained within canopy 26 when cage 20 is positioned thereincontamination due to gas exchange between adjacent cages is severelyreduced.

Shelf 14 is an air plenum which communicates with exhaust plenum 16 aswell as with gap h through openings 18 provided at the bottom of eachshelf 14. Openings 18 are positioned between canopy guides 26 tocorrespond with a position above and to the rear of each bonnet 24 ofeach cage 20.

Shelf plenums 14 communicate with rack exhaust plenum 16 through exhaustplenum ducts 16a. Exhaust plenum 16 may be connected with a barrier roomhouse exhaust system. Exhaust plenum 16 is a negative pressure plenum sothat air is drawn through openings 18 from above bonnet 24, throughshelf 14 in the direction of arrows A, through exhaust plenum duct 16aand into the house exhaust system through rack exhaust plenum 16. Air isdrawn from canopy 26 from around bonnet 24 removing contaminated airwhich escapes cage 20. By providing a ventilated rack and cage systemutilizing a negative pressure plenum in which air is drawn from a smallconfined space provided by canopy guides 26, an open ventilated rack isprovided which also provides for personnel protection as well as animalprotection.

In the simplest embodiment of the negative pressure ventilated cage andopen rack, no water is provided from an outside source to cages 20.Accordingly, water is provided from a supply positioned within the cage.As seen in FIGS. 1, 4 and 5, a wire bar lid 32 is positioned withinbottom portion 22 of each cage 20. A water bottle 33 is positionedtherein to supply water for animals contained within cage 20. Wire barlid 32 includes a plurality of wire bars 34 which form a holder forwater bottle 33 as well as extend to the top of sidewall 50 to besupported thereon and are sandwiched between bonnet 24 and sidewall 50to be maintained in place.

Conventional wire bar lids are constructed of wire bars having agenerally round cross-section so that a gap results between sidewall 50and bonnet 24. When air is removed from about Donnex 24 by negativepressure plenum 14, a Venturi effect occurs which causes air to movearound lip 28 of bonnet 24 breaking the cage level barrier. This air isthen drawn out of and away from the cage by the negative air flow ofplenum shelf 14. Accordingly, no product protection is provided eventhough personnel protection is provided. Experiments and use have alsoshown, that bedding and debris are discharged from the cage by theanimal activity within the cage. Accordingly, personnel protection maybe compromised during use of the conventional wire bar lid.Additionally, cross-contamination between cages occurs when bedding anddebris escapes one cage, contaminates the environment and enters anothercage.

Experiments have shown that by providing a thinned wire bar lid 32having a flattened perimeter frame 35 of a thin substantiallyrectangular cross-section for resting on bottom 22, the gap is reduced.This reduces the Venturi effect and aides in maintaining the cage levelbarrier of cage 20.

Reference is now made to FIGS. 11-14 in which wire bar lid, generallyindicated as 32, constructed in accordance with the invention is shownin detail. Bar lid 32 is formed of thin metal wire around the perimeterframe 35, i.e. perimeter 35 has a flat thin substantially rectangularcross-section. A skirt 90 extends from frame 35 at a substantially rightangle from frame 35 so as to be substantially parallel to upstandingwall 50 of bottom portion 22. Skirt 90 is integrally formed with frame35 forming a deflection barrier which extends around the entire top lip91 of bottom portion 22 when wire bar lid 32 is positioned in the bottomportion. A support flange 92 extends from skirt 90. The plurality ofwire bars 34 are attached to support flange 92 away from frame 35 andtop lip 91 of upstanding wall 50 of bottom portion 22.

In an exemplary embodiment, support flange 92, skirt 90 and frame 35 maybe formed as a single integral piece of stainless steel. Frame 35 isdimensioned to rest on lip 91 of bottom portion 22 of cage 20. Eachcorner of frame 35 is radiused to conform to the shape of cage 20. Wirebars 34 are welded to support flange 92. To facilitate providing feedand water, wire bar lid 32 includes containment ends 94 positioned ateither side of lid 32 as shown in FIG. 13. A divider 96 is rotatablymounted on a single wire 34 between end plates 94 to allow thesectioning of lid 32 when desired. Additionally, a protective plate 98is provided for receiving a water bottle.

By providing a wire bar lid having a flat perimeter and the lateralround wire bars supported below the perimeter of the lid, the perimeter,which is sandwiched between lip 28 and lip 91, substantially eliminatesthe gap between cage top 24 and cage bottom 22. This prevents the debrisand bedding kicked up by the animals within the cage from escaping fromcage 20 and reduces the Venturi effect on cage 20 thereby effectivelymaintaining the cage level barrier of cage 20.

By providing canopy guides 26, the air to be removed from the areasurrounding bonnet 24 is limited to that provided within gap h. Thiseffectively reduces the amount of air which must be removed whencompared to the prior art ventilated cage and rack which required thepassing of air across the tops of the cages rather than removal of airfrom each isolated cage 20. Accordingly, since a smaller area isutilized, the exhaust plenum may be operated at a lower air velocityutilizing less energy to provide the same function as in the prior artventilated rack.

In a second embodiment of the invention, the rack may be operated in apositive pressure mode. Air is input from a house supply system throughplenum 16 and flows in a direction opposite to that of arrows A throughplenum shelf 14 and openings 18. The air then surrounds bonnet 24 andremoves the air positioned above bonnet 2 4. Bonnet 24 includes a filtertherein so that the positive pressure air which flows into the cage isfiltered air. A Venturi effect is again created. In this case theVenturi effect also works to cause air to be blown through the gapprovided between bottom portion 22 and bonnet 24. However, this problemcan be alleviated by utilizing wire bar lid 32. Furthermore, the airbeing blown into the cage is only that which is within canopy 26,primarily the filtered air from shelf plenum 14. Therefore, no crosscontamination occurs. This embodiment provides product protection butdoes not provide personnel protection as air is blown out of ventilatedrack 12.

In a third embodiment provided in FIGS. 2, 3 and 7-10, positive airpressure is provided to each cage 20 through a second air supply systemand air is removed from cage 20 by negative air pressure applied througheach plenum shelf 14. Additionally, in an exemplary embodiment, a commonwater supply is utilized to transport water to each individual cage.Reference is specifically made to FIG. 2 wherein a transportingstructure, generally indicated at 36 for providing water and air to eachindividual cage 20 is provided. Transporting structure 36 includes awater manifold known in the art for delivering water to each cage 20.The water manifold includes a water source at one end and a drain at itsopposite end to provide a water flow path which traces a generallyserpentine path within rack 12 so that a pipe pair, generally indicatedat 38, formed by a first pipe 40 and a second pipe 44 is disposedadjacent and parallel to a respective shelf 14. Pipe pairs 38 areconnected to each other to form a water path between first pipe 40 andsecond pipe 44. Water travels from first pipe 40 through an elbow to asecond pipe 44 allowing water to pass each cage 20 of each shelf 14contained within rack 12. A number of female valve couplings 46 at leastequal to the number of cages 20 positioned within each rack 12 extendfrom first pipe 40 towards cage 20 at predetermined intervals.

Each bottom 22 is formed with a floor 48 and a wall 50 extendingtherefrom. As seen in FIG. 8 a recessed air diffuser 52 is formed inwall 50. A drinking valve 56 extends from air diffuser 52 within cage20. A male coupling valve 54 is dimensioned to be received by femalecoupling valve 46 causing female coupling valve 46 to open, thusallowing water to flow from pipe 40 to drinking valve 56.

An air plenum 58 is disposed between air supply plenum 74 at one end andcross bar 13 at the other end. Air plenum 58 is disposed about each pipepair 38 and traces a path substantially parallel to each plenum shelf14. A plurality of openings 60 are formed within air plenum 58 at eachfemale coupling valve 46 to allow female coupling valve 46 to extendtherethrough. As seen in FIG. 7, female coupling valve 46 is positionedwithin a docking cone 62. Docking cone 62 includes a cylinder 64 havinga docking portion 66 slideably mounted thereon. A spring 68 is disposedabout cylinder 64 for biasing docking cone 66 away from air plenum 58.Docking portion 66 has a diameter greater than recessed air diffuser 52and comes in contact with wall 50. Cylinder 64 is mounted at opening 60of air plenum 58 and forms an airtight seal therewith to provide an airconduit from air plenum 58 through docking portion 66 in a direction ofarrows B. The inner circumference 70 of docking cone 62 is greater thanthe outer diameter of female coupling valve 46 to allow room for air topass through docking cone 62. Air plenum 58 is coupled to a plenumsupply duct 74 through an opening 76 provided at each shelf providing anair path from air supply plenum 74 through opening 76 to air plenum 58.Air supply plenum 74 may be connected to the house air supply system.However, in an exemplary embodiment a cage air supply unit is providedon rack 12 which intakes room air, filters the room air and provides apositive air pressure air flow in a direction of arrows C and Dproviding a position pressure air flow through plenum 58 to each cage20.

As discussed above, at the location of each female coupling valve 46, aplurality of openings 60 are provided with air plenum 58 to allow air toescape from air plenum 58 to respective cages 20. Air plenum 58 is aclosed end air plenum receiving air from air supply plenum 74 whichtravels towards cross bar 13 forming the sealed end of air plenum 58. Asair travels along plenum 58, a portion of the air escapes throughopening 60, lessening the pressure of air plenum 60 so that a minimalpositive air pressure is provided at a cage 20 located at one end of arack compared to a maximum air pressure provided to a cage 20 providedadjacent supply plenum 74.

To balance the positive air pressure provided to each cage 20, thenumber of openings 60 located at each female coupling valve 46 arevaried. In an exemplary embodiment, seven docking positions areprovided. In a first group consisting of two docking positions closestto air supply manifold 74, eight openings 60 are provided within plenum58 at each docking position. A second group consisting of three dockingpositions which are next closest to air supply plenum 74 are eachprovided with a six hole pattern. The last two docking positions areprovided with a five hole pattern. Accordingly, the air flow balancingis accomplished by decreasing the number of holes within each pattern toprogressively increase the required outlet pressure at each dockingposition as the air flows from supply side of plenum 58 to the closedend of plenum 58. Additionally, by balancing each air supply location,the removal of any number of cages 20 from rack 12 does not affect theair balance to the remaining cages 20.

Reference is now made to FIGS. 1, 1a, 2, 3, 7 and 8 in which operationof the exemplary embodiment of the ventilated cage and rack system 10 isdefined. Female coupling valve 46 is positioned at a height to receivemale coupling valve 54 when cage 20 is slid into position resting on ashelf 14. The insertion of male coupling valve 54 opens female couplingvalve 46 providing water flow from pipe 40 to drinking valve 56.Drinking valve 56 remains closed until pressure is applied thereon by ananimal 76 when drinking, causing water to flow in the direction of arrowF. By providing water within each individual cage 20 upon drinking byeach individual animal, cross contamination caused by spilling ofdrinking water or the animal coming in contact with the environmentwithout cage 20 is severely reduced.

As seen in FIG. 8, spring 68 is compressible allowing docking portions66 to slide along cylinder 64. Additionally, spring 68 biases dockingportion 66 against sidewall 50 when cage 20 is moved towards air plenum58. When cage 20 is pushed towards air plenum 58 to engage femalecoupling valve 46 with male coupling valve 54 docking cone 62 iscompressed and cylinder 64 moves within recessed air diffuser 52 to forma substantially air tight gasket. Air flows in through opening 60 in thedirection of arrows B about a diffusion plate 78 through openings 80 ofair diffuser 52. Because the air is under positive pressure, the airwithin cage 20 is forced out of the cage through bonnet 24.Additionally, because air enters cage 20 through sidewall 50 of bottom22 it pushes the heavier ammonia and carbon diode particles which nestleat the bottom of cage 20 before the air and out around lip 28 thusreducing the level of gases as well as humidity within the cage, bettermaintaining the status of the animals contained therein.

The air that is forced about lip 28 fills gap h between bonnet 24 andshelf 14. Negative pressure plenum shelf 14 draws the air from thisspace through openings 18. The air is then exhausted through rackexhaust plenum 16. Accordingly, any contaminants which pass from cage 20are removed prior to coming in contact with any personnel. Thisembodiment provides both personnel protection and protection for theanimals contained within cage 20.

Canopy guides 26 also act to align male coupling valve 54 with femalecoupling valve 46. Canopy guides 26 are provided at positionscorresponding to female coupling valve 46 aligning with male couplingvalve 54. Male coupling valve 54 opens female coupling valve 46 byinsertion therein. Additionally, it is a friction fit which retains malecoupling valve 54 within female coupling valve 46 along with thefriction fit between canopy guides 26 and lower lip 28 of bonnet 24.Therefore, a slight amount of pressure in a direction coaxial with malecoupling valve 54 connects or disconnects male coupling valve 54 anddrinking valve 56 to or from female coupling valve 46 thus providing aquick release mechanism not requiring the touching of either couplingvalve, again reducing the occurrence of cross contamination as well asmaking the use of ventilated cage and rack system 10 more efficient andless time consuming.

To remove an individual cage 20 from rack 12, cage 20 is moved away fromplenum 58. This disconnects male coupling valve 54 from female couplingvalve 46 thus closing female coupling valve 46 preventing any leakage ofwater and resulting cross contamination. Because of the positivepressure cage air system in combination with the negative pressure racksystem, any contaminated air now in the rack is pulled through plenumshelf 14 and the status of the remaining cages 20 is not affected. Malecoupling valve 54 does not extend beyond the surface of wall 50,allowing bottoms 20 to be stacked for storage within each other andmaking then autoclavable.

Reference is now made to FIGS. 4, 5, 9 and 10 in which anotherembodiment of the invention is provided. In this embodiment, theventilated cage and rack 12 provides positive pressure air to each cage20 and removes air through negative pressure plenum shelf 14. Thesubstantial difference between the embodiments is that water is providedto the animals through a water bottle 34 supported in a wire bar lid 32.For simplicity, like numbers are utilized to indicate like structures.

A docking cone 62, having a docking portion 66 for coming in contactwith side walls 50 of cage 20 is affixed to plenum 58. A spring retainer84 is disposed within cylinder 64. Spring retainer 84 includes at leastone pair of leaf springs 86 extending from a base 85. Elbows 87 areformed on each leaf spring in facing relation to provide a narrowedspace therebetween.

Opening 60 within plenum 58 communicates with cylinder 64 of dockingcone 62 to allow air to pass through docking cone 62 in the direction ofarrows B. Additionally, cage 20 is provided with a recessed air diffuser52 disposed therein. A diffusion plate 78 is mounted on air diffuser 52.A plurality of holes 80 are formed within recessed air diffuser 52downstream of the air path from diffusion plate 78 to allow air to passfrom plenum 58, through cylinder 64 into cage 20. A screw 88 is mountedat the center of diffusion plate 78 and extends within recess airdiffuser 52.

During operation, cone 62 is again compressed against cage 20 as cage 20is moved towards air plenum 58. Elbows 87 of leaf springs 86 are forcedapart by screw 88 as screw 88 is inserted within docking cone 62. Sinceelbows 87 are integrally formed with leaf springs 86, elbows 87 arebiased towards each other gripping screw 88 to maintain cage 20 inplace. Docking cone 62 is compressed to form a substantially air tightgasket seal between air diffuser 52 and air plenum 58. Accordingly,filtered air flows in the direction of arrows B through openings 80 ofair diffuser 52. Again, because the air is under positive pressure theair within cage 20 is forced out of cage 20 around lip 28 of bonnet 24.This air is then removed by negative air pressure plenum shelf 14.Again, protection is provided for both the animal contained within cage20 as well as the personnel working with ventilated cage and rack system10.

The grip of elbows 87 about screw 88 is a simple tension fit. Since itis a simple tension fit which retains screw 88 within spring retainer84, only a slight amount of pressure is needed in a direction coaxialwith screw 88 to separate cage 20 from air plenum 58, thus providing aquick release mechanism.

Because of the positive pressure cage air system in combination with thenegative pressure rack system, any contaminated air now in the rack ispulled through negative pressure plenum shelf 14 and through air exhaustplenum 16 so that the status of the remaining cages 20 is not affected.Screw 88 does not extend beyond the surface of wall 50, allowing bottoms20 to be stacked for storage within each other and making themautoclavable.

The above explanations have been provided in connection with a singlesided ventilated rack for simplicity. However, the structure is equallyapplicable to a double sided ventilated rack in which the air plenum orair plenum and water manifold are disposed between the mirror sides ofthe double sided rack having docking cones and female coupling valvesextending in both directions from plenum 58.

Additionally, in an exemplary embodiment, rack 12 is mounted on wheels90 to allow portability from one area to another. A handle 92 is mountedon one side of rack 12 to aide in moving rack 12. Additionally, the useof a female coupling valve as the connection to the water manifold is byway of example only. The female coupling valve may extend from arecessed air diffuser to couple with a male coupling valve extendingfrom the water manifold.

Accordingly, by providing a ventilated cage and rack system whichdelivers positive pressure air to the cage while confining the airexhaust from the cage to a limited area and providing a negative airpressure plenum which communicates with that area, both animalprotection and personnel protection is provided in a ventilated cage andrack system. Additionally, such a configuration makes it possible toutilize an open rack ventilated cage and rack system.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description, are efficiently attained and,since certain changes may be made in the above construction withoutdeparting from the spirit and the scope of the invention, it is intendedthat all matter contained in the above description and shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

It is also to be understood that the following claims are intended tocover all the generic and specific features of the invention hereindescribed and all statements of the scope of the invention which, as amatter of language, might be said to fall therebetween.

What is claimed is:
 1. A wire bar lid for use in animal cage having abottom portion and a filter bonnet, said wire bar lid comprising aperimeter having a length, a portion of said perimeter defining a flatsurface for receiving a filter bonnet, a plurality of wire barssubstantially extending in a lengthwise direction parallel to the lengthof said perimeter at substantially spaced intervals, each of said barsbeing supported within said perimeter, whereby said wire bar lid isadapted to be positioned between said filter bonnet and bottom portion,said perimeter limiting any openings formed between said filter bonnetand bottom when said filter bonnet is placed upon said bottom a skirtextending from said perimeter at a substantially right angle, a supportflange affixed to said skirt, said plurality of wire bars beingsupported on said support flange so that said wire bars are supportedbelow said perimeter; said cage being a cage level barrier cage.
 2. Awire bar lid for use in an animal cage having a cage bottom and a cagebonnet, said wire bar lid comprising a frame adapted to be supported bya cage bottom; a skirt extending from said frame at a substantiallyright angle, a support flange affixed to said skirt, a plurality of wirebars extending the length of said frame at substantially parallel spacedintervals; said plurality of wire bars being supported on said supportflange so that said bar wires are supported below said frame and withinthe cage bottom when the wire bar lid is supported by the cage bottom.3. The wire bar lid of claim 2, wherein said frame, said skirt and saidsupport flange are integrally formed with each other as a unitarymember.
 4. The wire bar lid of claim 2, wherein said bonnet is formedwith a lip, said lip being dimensioned to receive said cage bottom andrest thereon, said frame being dimensioned to be disposed between saidlip and said cage bottom.